/*
 * Copyright (c) 2018,2019 Contributors to the Eclipse Foundation
 *
 * See the NOTICE file(s) distributed with this work for additional
 * information regarding copyright ownership.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * You may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.eclipse.microprofile.context.tck.contexts.buffer.spi;

import java.util.concurrent.atomic.AtomicBoolean;

import org.eclipse.microprofile.context.spi.ThreadContextController;
import org.eclipse.microprofile.context.tck.contexts.buffer.Buffer;

/**
 * Restores a buffer context that was saved upon creation.
 */
public class BufferContextRestorer implements ThreadContextController {
    private StringBuffer bufferToRestore = Buffer.get();
    private AtomicBoolean restored = new AtomicBoolean();

    /**
     * Restore the buffer context that was saved upon construction of this instance.
     */
    @Override
    public void endContext() {
        if (restored.compareAndSet(false, true)) {
            Buffer.set(bufferToRestore);
        } else {
            throw new IllegalStateException();
        }
    }

    // For easier debug
    @Override
    public String toString() {
        return "BufferContextRestorer@" + Integer.toHexString(System.identityHashCode(this)) +
                " for StringBuffer@" + Integer.toHexString(System.identityHashCode(bufferToRestore)) +
                ": " + bufferToRestore.toString();
    }
}
